Brake system with antiskid control

Abstract

The brake system includes a master cylinder having a master-cylinder piston slidable in a working chamber, a power source and a pressure-control valve disposed in axial alignment with the piston. The pressurized fluid of the power source controlled by the control valve is directed to the wheel brake cylinders via the working chamber without displacement of the piston. This arrangement makes it possible to operate the wheel brake cylinders by the power source without actuating the piston. The piston is actuated only if the power source fails. An antiskid control system is disposed in the hydraulic lines between the working chamber and the wheel brake cylinders. A hydraulic valve arrangement is disposed in return lines from the antiskid control system to an unpressurized reservoir to deactivate the antiskid control system when the power source fails.

I claim: 
     
       1. A full power braking system with an antiskid control comprising: a master cylinder including a housing having a longitudinal axis,   a first working chamber disposed in said housing coaxial of said axis,   a first piston coaxial of said axis slidable in said first working chamber in response to a brake pedal depression;     a power source coupled to said master cylinder;   wheel brake cylinders coupled to said first working chamber;   a pressure-control valve disposed in said master cylinder coaxial of said axis associated with said power source to control fluid from said power source to actuate said wheel brake cylinders from said first working chamber without displacing said first piston;   an antiskid control system disposed between said first working chamber and said wheel brake cylinders; and   a device in said master cylinder to interrupt a connection between said first working chamber and said power source when said first piston is displaced in the actuating direction upon failure of said power source.   
     
     
       2. A system according to claim 1, wherein said pressure-control valve connects said power source to said wheel brake cylinders through said first working chamber.   
     
     
       3. A system according to claim 1, wherein said pressure-control valve generates a pressure in a line connecting said wheel brake cylinders with said power source through said first working chamber by throttling the flow of said fluid.   
     
     
       4. A system according to claim 1, wherein said first piston includes a sleeve seal disposed at the end of said first piston in said first working chamber engaging the inner surface of said housing,   another seal between the outer surface of said first piston and the inner surface of said housing from said sleeve seal toward said brake pedal,   an annular chamber disposed between the outer surface of said first piston and the inner surface of said housing and between said sleeve seal and said another seal, said annular chamber being connected to said power source by said pressure-control valve, and   a fluid connection between said annular chamber and said first working chamber provided by longitudinal bores spaced from said axis in said first piston and past the outer periphery of said sleeve seal.     
     
     
       5. A system according to claim 4, wherein said master cylinder further includes a pressure-tight reservoir disposed in said housing adjacent said working chamber,   a bore disposed in said housing connecting said annular chamber to said reservoir, and   a compensating bore disposed in said housing connecting said working chamber to said reservoir.     
     
     
       6. A system according to claim 5, wherein said reservoir is connected to an unpressurized reservoir by said pressure-control valve when said brake system is not activated.   
     
     
       7. A system according to claim 1, wherein said first piston includes a longitudinal bore coaxial of said axis; and said pressure-control valve includes   a valve spool rigidly connected to said brake pedal and slidably guided in said longitudinal bore.     
     
     
       8. A system according to claim 1, wherein said first piston includes a sleeve seal disposed at the end of said first piston in said first working chamber engaging the inner surface of said housing,   another seal between the outer surface of said first piston and the inner surface of said housing spaced from said sleeve seal toward said brake pedal,   an annular chamber disposed between the outer surface of said first piston and the inner surface of said housing and between said sleeve seal and said another seal, and   a fluid connection between said annular chamber and said first working chamber provided by longitudinal bores spaced from said axis in said first piston and past the periphery of said sleeve seal;     said master cylinder further includes a pressure-tight reservoir disposed in said housing adjacent said first working chamber,   a first bore disposed in said housing connecting said annular chamber to said reservoir, and   a second bore disposed in said housing connecting said first working chamber to said reservoir; and     said pressure-control valve includes a throttle member connected to said brake pedal; and further including     an unpressurized reservoir; and   a fluid connection between said pressure-tight reservoir and said unpressurized reservoir including said first bore,   said annular chamber,   a third bore in said first piston connected to said annular chamber,   a longitudinal bore coaxial of said axis in said first piston connected to said third bore,   an outlet port of said longitudinal bore adjacent said throttle member,   a fluid chamber in said housing connected to said outlet port, and   a line connecting said fluid chamber to said unpressurized reservoir;     said throttle member throttling said outlet port upon actuation of said brake pedal to generate pressurized fluid in said first working chamber to actuate said wheel brake cylinders.   
     
     
       9. A system according to claim 1, wherein said pressure-control valve includes a control casing slidable in said housing in the actuating direction disposed coaxially of said axis between said brake pedal and said first piston in tandem relation with said first piston,   a simulator spring disposed coaxial of said axis between said first piston and said control casing, and   a valve spool rigidly connected to said brake pedal disposed coaxial of said axis within said control casing.     
     
     
       10. A system according to claim 9, wherein said first piston includes a first sleeve seal disposed at the end of said first piston in said first working chamber engaging the inner surface of said housing,   a first seal between the outer surface of said first piston and the inner surface of said housing spaced from said first sleeve seal toward said brake pedal,   a first annular chamber disposed between the outer surface of said first piston and the inner surface of said housing and between said first sleeve seal and said first seal, and   a first fluid connection between said first annular chamber and said first working chamber provided by first longitudinal bores spaced from said axis in said first piston and past the periphery of said first sleeve seal; further including       a chamber defined by the brake pedal end of said control casing and the brake pedal end of said housing; and   a first longitudinal channel in said housing spaced from said axis to feed pressurized fluid from said power source from said chamber to said first annular chamber under control of said valve spool.   
     
     
       11. A system according to claim 10, further including a second piston disposed in said housing coaxial of said axis remote from said brake pedal and in tandem relation with said first piston;   a second working chamber defined by the end of said second piston remote from said first piston and the end of said housing remote from said brake pedal;   said second piston including a second sleeve seal disposed at the end of said second piston in said second working chamber engaging the inner surface of said housing,   a second seal between the outer surface of said second piston and the inner surface of said housing spaced from said second sleeve seal toward said first piston,   a second annular chamber disposed between the outer surface of said second piston and the inner surface of said housing and between said second sleeve seal and said second seal, and   a second fluid connection between said second annular chamber and said second working chamber provided by second longitudinal bores spaced from said axis in said second piston and past the periphery of said sleeve seal; and     a second longitudinal channel in said housing spaced from said axis connected to said first longitudinal channel to feed pressurized fluid from said power source from said chamber to said second annular chamber under control of said valve spool.   
     
     
       12. A system according to claim 11, wherein said first piston is a stepped piston, and   said first annular chamber includes an actuating surface adjacent said brake pedal having a larger diameter than a surface of said first annular chamber adjacent said piston; and further including       a stop in the inner surface of said housing adjacent said brake pedal against which said first piston rests.   
     
     
       13. A system according to claim 12, wherein said second piston has a smaller diameter than said first piston and said second piston is secured to said first piston.   
     
     
       14. A system according to claim 13, wherein said antiskid control system includes at least two antiskid control units, one of said units being connected between said first working chamber and certain ones of said wheel brake cylinders and the other of said units being connected between said second working chamber and others of said wheel brake cylinders, each of said units having a return line to an unpressurized reservoir to remove pressurized fluid from said wheel brake cylinders upon receiving a signal indicating an impending wheel lock; and further including       a hydrualic locking arrangement connected to said power source and in said return lines including two valve spools held in a first position by energy from said valve source against the force of springs each connected to a different one of said two valve spools, said first position permitting pressurized fluid to flow from said units to said unpressurized reservoir, said two valve spools being moved to a second position by said springs upon failure of said power source to block flow from said units to said unpressurized reservoir.     
     
     
       15. A brake system according to claim 1, further including a hydraulic locking arrangement disposed in return lines from said antiskid control system to an unpressurized reservoir to deactivate said antiskid control system upon failure of said power source.   
     
     
       16. A brake system according to claim 15, wherein said locking arrangement includes a valve arrangement blocking said return lines upon failure of said power source.